Improvement of the engineering properties of granular soil using bacteria

• Main Author: Wong, Dun Yi.
• Other Authors: Chu Jian
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Civil engineering::Geotechnical
• Online Access: http://hdl.handle.net/10356/40204
• Institution: Nanyang Technological University

It has always been the goal of civil engineers to improve the mechanical engineering characteristics of ground material. From retaining earth works, embankments, land reclamation to remedial shoring up of excessive settlement under existing structures and reduction of liquefaction potential in earthquake-prone areas. Previously, mechanical methods have always been the primary means of doing so. Many of these methods are cost and energy intensive. On top of that, they are generally pre-construction phases and are unable to be used as remedial means. Chemical grouting allows utilisation which overcomes some of this limitations, but is generally toxic and unsuitable for use due to environmental impact. In light of these considerations, microbial modes of improving the mechanical characteristics have been investigated in recent years. In the past few years, it has been shown that bioclogging and biocementation have displayed great promise in altering soil characteristics with potentially lower ecological impact at a lower cost. Via different mechanisms, these techniques have sought to utilise commonly found bacteria to facilitate the improvement of soil properties. For biocementation, the most documented process is urea hydrolysis mediated calcite precipitation. The focus of these experiments would be biocementation utilising denitrification bacteria. There are possible advantages of the denitrification process as compared to the urea hydrolysis. Key factors such as type of bacteria, time needed, application in situ, substrates, by-products as well as long-term stability has to be investigated before commercial usage. The experiments will determine the optimal dosage of substrate as well as type of soil conditions which it can be used under. Also shown, will be an increase in the mechanical properties of granular soil.